In a decomposition reaction, what occurs to a single compound?

In a decomposition reaction, a single compound is broken down into simpler substances. This process typically involves the breakdown of chemical bonds within the compound, leading to the formation of two or more products that are often elements or simpler compounds.

For instance, when water (H₂O) undergoes decomposition, it can break down into hydrogen gas (H₂) and oxygen gas (O₂) through the application of energy, such as heat or electricity. This is a classic example of a decomposition reaction where the original compound loses its identity and can no longer be observed in its original form.

The other options describe incorrect concepts: forming a new compound suggests a combination or synthesis reaction rather than the breakdown that characterizes decomposition. Reacting with another compound describes a different type of chemical reaction where two substances interact to form products, rather than the breakdown of a single entity. Lastly, remaining unchanged contradicts the very definition of decomposition, which inherently involves change.